As wireless technology develops, in order to enhance and provide new capabilities and to accommodate increased usage, there is a constant need to improve data rates and efficiency of data transmission over wireless networks. Different standards have attempted to address this need in various ways. In recently developed LTE standards, for example, one approach to increase data rates is the use of so-called carrier aggregation (CA). In carrier aggregation, two or more component carriers (frequency blocks used for communications) are aggregated and jointly used for transmission to/from a single mobile terminal (also referred to as user equipment or “UE”). When carrier aggregation is initiated, a primary serving cell (PCell) can be initially configured to a UE by eNodeB and subsequently secondary serving cells (SCell) can also be added to this UE by eNodeB, which may serve to increase data rates.
In particular, multiple component carriers (CC) can be aggregated to support wider transmission bandwidths, for example, up to 100 MHz, in presently envisioned schemes. For example, in LTE-A (3rd Generation Partnership Project, Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) (release 10), June 2011), two component carriers may be aggregated to form a 40 MHz bandwidth for frequency division duplex (FDD) or time division duplex (TDD) schemes. For LTE Rel-10 TDD system, only the intraband carrier aggregations are supported, wherein physical uplink control channel (PUCCH) is transmitted on one primary cell (PCell) and wherein the UL-DL configurations shall be the same, while in developing standards, such as LTE Release 11, the interband carrier aggregations can be supported with the different UL-DL configurations on the interband carrier frequencies. In one possible approach, intraband carrier aggregation may group multiple carriers within a band. Such intraband carrier aggregation can be applied to both frequency division duplex (FDD) and time division duplex (TDD) schemes. Another possibility is the so-called interband carrier aggregation, in which carriers between different bands are aggregated. The interband carrier aggregation, when used for TDD system, may include different uplink-downlink (UL-DL) configurations on different bands. However, the uplink subframes and downlink subframes may overlap on different UL-DL configurations of the interband carrier frequencies. This may compromise the ability to send control messages such as acknowledgement/non-acknowledgement (ACK/NACK) messages because of the conflict in timing for the control messages. For example, in response to downlink transmissions that may take place over a physical downlink shared channel (PDSCH), the UE provides a feedback ACK/NACK message via an uplink channel, such as a physical uplink control channel (PUCCH) or physical uplink shared channel (PUSCH). In an interband aggregation scenario, the PDSCH transmission may be sent over a secondary serving cell, or secondary cell (SCell) in a given sub-frame. However, the communications protocols, such as those specified in LTE release 10, may require the feedback of the ACK/NACK message to take place on the primary serving cell (also termed primary cell or Pcell) only, which may have a different UL-DL configuration from the SCell, meaning that the uplink sub-frames and downlink subframes are arranged in a different UL-DL configuration within a radio frame. Therefore, in some cases of interband carrier aggregation, the uplink ACK/NACK message can not be transmitted because, unlike in the subframe arrangement in the Scell, the given sub-frame of a primary cell (PCell) required to carry the feedback may be a downlink rather than the required uplink.
It is with respect to these and other considerations that the present improvements have been needed.